UNIT
B
Self-Quiz
SUGGESTED ANSWERS
1.
(b); Choice (d) is correct because producers can make their own food compounds, but consumers cannot.
Choice (a) is incorrect because no organisms can cycle energy. Choices (c) and (d) are incorrect because
both are processes that producers and consumers do.
2.
(c); Choice (c) is correct because an ecological niche is the term used to describe the unique role of a
species in its habitat. Choice (a) is incorrect because a trophic level is a feeding level of a food chain.
Choice (b) is incorrect because a feeding role is a term to describe the way an organism gets energy
(consumer, producer, decomposer). Choice (d) in incorrect because a food chain shows the path of energy
as it moves through organisms in a community.
3.
(b); Choice (b) is correct because plants are biotic, not abiotic, factors. Choices (a), (c), and (d) are
incorrect because they are examples of abiotic factors.
4.
(d); Choice (d) is correct because pesticides can pass from organisms in one trophic level to organisms
in the next trophic level. Choice (a) is incorrect because pesticides can harm or kill non-target species in
addition to the target species. Choice (b) is incorrect because pesticides tend to reduce crop damage and
increase overall food production. Choice (c) is also incorrect. Fertilizers, not pesticides, are used to replace
nutrients in soil.
5.
False. Primary succession occurs in an area where no organisms have lived previously, and typically begins
on soil or bare rock. Secondary succession occurs in areas that have been partially disturbed, but not
destroyed. A true version of the statement would be: Secondary succession occurs in an ecosystem that has
been partially disturbed by an event such as a forest fire.
6.
False. Fragmentation reduces sustainability because areas are more exposed to damaging influences, such
as pollution. A true version of the statement would be: Fragmentation of an ecosystem occurs when the
ecosystem is divided into smaller parcels, making it less sustainable.
7.
True. Threatened species are not yet endangered, but will likely become endangered if conditions do not
improve. A species of special concern is not yet threatened or endangered.
8.
leaching; Leaching occurs when nutrients, such as nitrogen compounds from fertilizers, become dissolved
in water and seep out of the soil. The nutrients then enter the groundwater and contaminate it.
9.
ecosystem; By definition, an ecosystem includes all of the biotic and abiotic factors in an area.
10. (a)(v)
Producers get energy making their own food; (b)(ii) Consumers get energy by eating other
organisms; (c)(iv) Decomposers get energy by eating dead organisms and animal waste; (d)(vi) A food
chain shows a sequence of organisms in a linear progression, each feeding on the next; (e)(iii) A food web
shows a network of feeding relationships within a community and is not shown as a linear progression;
(f)(i) A trophic level is the feeding level of an organism in an ecosystem.
11.
Sample answer: Three examples of products we obtain from terrestrial ecosystems are maple syrup, rubber,
and wax.
12.
A population is a group of organisms of the same species living in the same area at the same time. A community
is made up of all the populations in an area.
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13. (a)
(b)
Predation and parasitism are both interactions between individuals of different species. In both cases,
one organism benefits, whereas the other is harmed.
In predation, the organism that is harmed dies and is used for food by the predator. In parasitism, the
organism that is harmed (the host) typically does not die because the parasite needs its host to remain
alive in order to continue benefiting from it.
14.
Sample answer: Plant 100 sugar maples on two equal-sized plots of land in the same area so that the
conditions are identical. Both plots should receive acid precipitation as part of the control conditions.
Add the fertilizer that claims to add calcium back into the soil to only one of the plots. After a set period
of time, compare the differences between the two plots and test the soil for calcium levels.
15.
Sample Answer: Eating lower on the food chain is an energy-efficient practice due to the loss of energy at
each trophic level of the food chain. For example, eating corn at the first trophic level of the food chain avoids
the energy loss that occurs when human consume chickens that have consumed corn.
16.
Sample answer: Turning the forest into farmland area would cause habitat loss for the organisms currently
living in this forested area. Farmland also typically consists of monocultures, which alter ecological cycles
and reduce biodiversity. In addition, the crops grown on farms are typically non-native species that attract
pests and require both heavy fertilizer and pesticide use, both of which have negative impacts on the
surrounding environment.
17. (a)
(b)
18. (a)
(b)
19. (a)
(b)
The soil is compacted from foot traffic, making it difficult for plants to grow because the roots cannot
get water or air.
Walking off of the trails would compact soil in more places. This would make it more difficult for
plants to grow in that soil.
Sample Answer: The temperate deciduous forest biome would be the most successful for farming because
it has a long growing season, moderate amounts of rainfall, moderate temperatures, and fertile soil.
Sample answer: It would be very difficult to farm in the tundra biome. The soil is of poor quality and
the growing season is very short.
When organisms die, decomposers break them down into basic nutrients, such as carbon, oxygen, and
nitrogen. The decomposers put these nutrients back into the soil where producers can use them to grow.
If decomposition did not occur, matter would stop cycling. The plants would not have the necessary
nutrients to grow and eventually all living things would die.
20. (a)
One of the major roles of trees in the water cycle is to take in water from the ground and release it back
into the air through transpiration. When deforestation occurs, less water is returned to the atmosphere
(because transpiration is not occurring). As a result, fewer rain clouds form, leading to less rainfall. Over
time drought conditions can occur in this area and eventually the area may become a desert.
(b)
Fewer trees would be available to absorb carbon dioxide. As a result, more carbon dioxide would remain in
the atmosphere. In addition, the cutting down of trees would release carbon dioxide into the atmosphere.
(c)
In the nitrogen cycle, plants take up nitrogen from the soil. The nitrogen becomes incorporated into
the plants’ tissues, which then allows nitrogen to move through the food chains and food webs in the
ecosystem. If massive deforestation occurred, the amount of nitrogen taken out of the soil and made
available to consumers would greatly decrease.
21. (a)
(b)
22.
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The population of producers on the island would likely increase because there would be fewer
herbivores to eat them.
Herbivores are first-level consumers, which are eaten by secondary consumers. If the population of
herbivores is halved, the secondary consumer population will also diminish, due to a decrease in their
food supply.
Sample Answer: Three questions I might ask are: (1) Do you know that you are harming the environment
by clear-cutting forests? (2) What benefits do you expect to receive from having this farmland? (3) Do you
know any alternatives to clear-cutting, and if so, why did you not use these alternatives?
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23.
In the winter, deciduous trees do not carry out photosynthesis, which means that much less carbon dioxide
is taken in from the atmosphere. This would account for the higher levels during the winter. In the spring
and summer, trees are photosynthesizing at high levels and therefore taking larger amounts of carbon
dioxide out of the atmosphere.
24.
The ratio of predator to prey in the community with the lion would be lower because a lion needs much
more food to sustain it than an alligator does. For example, if the ratio of lions to prey is 1 to 500, then
the ratio of alligators to prey might be 1 to 100.
25. (a)
Sample food web:
polar bears
beluga whales
ringed seals
walruses
arctic cod
zooplankton
phytoplankton
(b)
Producers: phytoplankton
Primary consumers: zooplankton
Secondary consumers: Arctic cod
Tertiary consumers: beluga whales, ringed seals, walruses
Quaternary consumers: polar bears
(c)
There are so few polar bears in Arctic ecosystems because energy is lost at each trophic level; therefore
very little energy of the original energy remains at the higher trophic levels.
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